First measurement of the ϱ spectral function in nuclear collisions

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size close to 400000 events and the good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution from π⁺π^-→ϱ→μ⁺μ^- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The p_T-differential mass spectra show the excess to be much stronger at low p_T than at high p_T. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to the chiral condensate. PACS 25.75.-q; 12.38.Mh; 13.85.Qk     

Improvement of the detection limit of carbon in metal alloys by Ion Microprobe Analysis

Summary An important aim of materials research is the detection of dependencies between local carbon distributions and mechanical characteristics. Because of the small concentration of carbon the methods of analysis for the detection of local element distributions-e.g. Auger Spectroscopy, Electron Microprobe, and Ion Microprobe Analysis-are not directly suitable.This paper presents results of examinations with Ion Microprobe Analysis which improve the detection limit of carbon by a factor of 100. Thus the aim to detect local distributions of carbon in high temperature alloys seems to be possible for concentrations above 200 ppm.

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Verbesserung der Nachweisgrenze für Kohlenstoff in Metallegierungen mit Hilfe der lonenmikrosonden-Analyse

Zusammenfassung Ein wichtiges Ziel der Werkstofforschung ist der Nachweis von Abhängigkeiten zwischen lokalen Kohlenstoffverteilungen und mechanischen Werkstoffeigenschaften. Wegen der kleinen Kohlenstoffgehalte sind die Verfahren zur Bestimmung lokaler Elementverteilungen — Auger-Spektroskopie, Elektronenmikrosonde und Ionenmikrosonde — nicht direkt geeignet. Es werden Untersuchungsergebnisse angegeben, die eine Verbesserung der Nachweisgrenze für Kohlenstoff mit der Ionenmikrosonde um den Faktor 100 ermöglichen. Damit erscheint der Nachweis lokaler Kohlenstoffverteilungen in Hochtemperaturwerkstoffen für Konzentrationen 200 ppm möglich.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

用于ECR离子源的超导磁体——设计与制造

Superconducting magnets are widely used in ECR ion sources.The intensity and form of the magnetic field plays an important role in the way towards higher performance sources.During the development steps,the design principles and geometries had to be adapted to reach higher fields using state-of-the-art technologies and design tools.Production,assembly,and tests of these superconducting magnets are presented and a short outlook on possible future developments is given.     

Extraktionsapparate

Ohne Zusammenfassung     

An optimal software debugging model

This paper deals with the question of optimal debugging times for large-scale computer programs, given certain assumptions concerning the distribution of error within the program, the cost that is incurred whenever a fault occurs, and the cost of debugging. Modeling takes place within the framework of independent Poisson processes describing faults caused by errors. The optimization aim is to minimize the long-run total expected discounted cost. Some general results concerning the optimal polity are presented.This research has been supported by NATO Grant No. RG.86/0024, by the Alexander von Humboldt Foundation, and by the University of Passau, Germany.     

Running time experiments on some algorithms for solving propositional satisfiability problems

Satisfiability problems are of importance for many practical problems. They are NP-complete problems. However, some instances of the SAT problem can be solved efficiently. This paper reports on a study concerning the behaviour of a variety of algorithmic approaches to this problem tested on a set of problems collected at FAW. The results obtained give a lot of insight into the algorithms and problems, yet also show some general technical and methodological problems associated with such comparisons.     

J/psi production in Indium-Indium collisions at 158 GeV/nucleon

The NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of J/psi in In-In collisions. We have studied the J/psi centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than approximately 80 participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results.